Recently, due to the advantages of simple, light and low cost, the touchpad has been widely applied in various electronic products to replace the conventional input devices, for example the computer mouse. A method and apparatus for scroll bar control is proposed by U.S. Pat. No. 5,943,052 to Allen et al., to define scroll regions on a touchpad for scrolling the scroll bars of a window. Specifically, as shown in FIG. 1, on a touchpad 10 there are a block 12 to be defined for cursor control region, a block 14 to be defined for vertical scroll region, and a block 16 to be defined for horizontal scroll region. When a user is to move a cursor, he needs to put his finger in the cursor control region 12 first, and then to move his finger in the cursor control region 12 to control the movement of the cursor. When a user is to scroll a window in the vertical direction, he is requested to put his finger in the vertical scroll region 14 first, and then to vertically move his finger in the vertical scroll region 12 to control the vertical scroll bar of the window. Similarly, to scroll a window in the horizontal direction, a user is requested to put his finger in the horizontal scroll region 16 first and then to horizontally move his finger in the horizontal scroll region 16. However, defining the vertical scroll region 14 and the horizontal scroll region 16 will reduce the area of the cursor control region 12, and therefore have the operations in the cursor control region 12 more difficult. Moreover, the vertical scroll region 14 and the horizontal scroll region 16 cannot be enabled to use at a same time. Further, each time to switch between the cursor control function and the scroll bar control functions, for example from the cursor control function to the vertical scroll bar control function or from the vertical scroll bar control function to the horizontal scroll bar control function, the user is necessary to have his finger leaving the touchpad 10 from the current region first and then touching on the touchpad 10 in another region again, to terminate the current control function and to start up the next control function. For example, slipping the finger on the touchpad 10 from the cursor control region 12 to either the vertical scroll region 14 or the horizontal scroll region 16 will not enable any scroll bar control functions. More disadvantageously, to avoid the finger to put in a wrong region when switching between difference control functions, the user needs to move his eyes from the monitor to the touchpad 10 to ensure the position where his finger is touching on again and again.
On the other hand, a method is proposed by U.S. Pat. No. 5,825,352 to Bisset et al., by sensing the number of fingers landing on a touchpad to emulate mouse buttons and mouse operations. However, this art cannot provide any scroll bar control functions by operating on a touchpad.
Therefore, it is desired a method using multiple fingers for scroll bar control on a touchpad.